The first communities to move into disturbed or vacated volumes of space or areas of a planet which have been abandoned or devastated.

Species of plants and other organisms moving in to colonise an area left empty by forest fire, flood or the relocation of sentient habitation; a clade moving into a volume vacated due to mass transcension as in the area vacated by Ethonos and the Church of the Eye, or sterilisation as in the area devastated by the Verifex supernovae.

These clades and species are necessarily transient, often fugitive: after a period of time more robust or advanced or competitive clades or species will form the next sere or society in the ecological/toposophic progression.